The present invention relates to a gas shut-off valve which can be triggered by an earthquake.
There is a greater danger of explosion and fire due to broken gas lines as a result of an earthquake. The famous San Francisco earthquake of April 18, 1906 is often remembered as the great San Francisco fire. The earthquake damage in San Francisco has been estimated at $20,000,000 and the fire damage at $400,000,000. This illustrates the fire danger in earthquake areas. An automatic valve which cuts off the gas flow when activated by an earthquake could save lives and property.
The intensity of horizontal acceleration which is considered damaging for structures varies with geographical zones. The State of California specifies 0.133 of gravity. Other states have lower values. The valve should be able to react to any predetermined horizontal acceleration. Also, the horizontal accelerations produced by an earthquake may be in any direction, therefore, the valve should be equally sensitive in any direction.
After an earthquake or any other disturbance which triggered the valve, it may be desirable to reset the valve to the open position and re-establish the gas flow. This operation should be easily accomplished by unskilled persons.
The valve should not be easily triggered to the closed position, either by accident or intentionally. The repeated actuation of the re-setting mechanism should not disturb the valve once it is set in the armed position.
It is an object of the present invention to provide a simple, inexpensive valve, which will shut off the gas flow when it is triggered by an earthquake which reaches a certain magnitude in any horizontal direction.
Another object is to provide a simple mechanism for re-setting the valve to the armed position and re-establish the gas flow.
Another object is to provide a re-setting mechanism which will not disturb the valve once it is set in the armed position.
Another object is to provide a rugged valve made of durable materials which will not corrode or deteriorate over the years, so the valve will be effective to cut the passage of gas in case of an earthquake and the re-setting mechanism will be operational even after years of inactivity or after repeated operation.
Another object is to provide the minimum number of movable parts which are critical for the reliable accomplishment of the shut-off cycle, and this has been achieved by having only one moving part, a ball.